Towards Understanding Non-Equilibrium Systems

Balance is a goal many wish to achieve, and that is not limited to people. Many physical systems try to achieve balance or equilibrium, but many also must exist in a state of non-equilibrium to function. Such non-equilibrium systems are not well understood in part because of the limitations on creating them, but researchers at Northwestern University have found a new way to do so.

A system at equilibrium has no potential and no energy, as any change in one direction is met by a change in the other. A non-equilibrium system is constantly changing though, as energy is continually being added. Examples of such systems include the Earth's plate tectonics, airplanes, and even the human body. Theoretically, the constant adding of energy will allow structures to be formed within a non-equilibrium system, and the Northwestern researchers found a way to test this. They made a mixture of pH-responsive particles, which will change their electric charges when pH levels are altered. This oscillation provides the energy input needed to form the non-equilibrium structures predicted.

As you may be able to guess, non-equilibrium structures are impossible to create under equilibrium conditions. This discovery could enable these structures to be designed by scientists, by tuning the oscillations adding the necessary energy.